BMW 335D AdvancedDiesel with BluePerformance.pdf

8/10/2019 BMW 335D AdvancedDiesel with BluePerformance.pdf

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BMW Service

Technical Training -Product Information.Advanced Diesel with

BluePerformance.


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The information contained in the Product Information and the Workbook form an integral part ofthe training literature of BMW Technical Training.

Refer to the latest relevant BMW Service information for any changes/supplements to theTechnical Data.

Information status: June 2008

Contact: [email protected]

2008 BMW AGMnchen, GermanyReprints of this publication or its parts require the written approval ofBMW AG, MnchenVH-23, International Technical Training


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Product Information.Advanced Diesel.

Diesel engine for North America

Selective Catalytic Reduction (SCR)

Low pressure exhaust gas recirculation(LP EGR)


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Notes on this Product Information

Symbols used

The following symbols are used in this Product Information to improveunderstanding and to highlight important information:

3 contains important safety information as well as information that isnecessary to ensure smooth system operation and must be adhered to.

1identifies the end of a note.

Information status and national variants

BMW vehicles conform to the highest safety and quality standards.Changes in terms of environmental protection, customer benefits anddesign render necessary continuous development of systems andcomponents. Consequently, there may be discrepancies between thisProduct Information and the vehicles available in the training course.

This documentation describes left-hand drive vehicles.In right-hand drive vehicles, the arrangement of some controls orcomponents may differ from the illustrations in this Product Information.Further differences may arise as the resultof theequipmentvariants used

in specific markets or countries.

Additional sources of information

Further information on the individual topics can be found in the following:

- Owner's Handbook

- Integrated Service Technical Application.


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Contents.Advanced Diesel.

Objectives 1Product information and working reference forpractical applications. 1

Models 3Engine variants 3

Introduction 7

System components 23Engine mechanical system 23Air intake and exhaust system 25Cooling system 38Fuel preparation system 41

Overview of fuel supply system 43Functions of the fuel supply system 47Components of the fuel supply system 51Overview of selective catalytic reduction 60Functions of selective catalytic reductionsystem 72Components of the selective catalyticreduction system 95Engine electrical system 110

Automatic transmission 119


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Objectives.Advanced Diesel.

Product information and working reference for practicalapplications.

This Product Information provides informationon the design and function of the M57D30T2US engine.

This Product Information is structured as aworking reference and complements thesubject material of the BMW AftersalesTraining seminar. The Product Information isalso suitable for self-study.

As a preparation for the technical trainingprogram, this Product Information provides an

insight into the diesel engine for the USmarket. In conjunction with practical exercisescarried out in the training course, its aim is toenable course participants to carry outservicing work on the M57D30T2 US engine.

Technical and practical backgroundknowledge of thecurrent BMW dieselengineswill simplify your understanding of thesystemsdescribed here and their functions.


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Models.Advanced Diesel.

Engine variants

Models with the M57D30T2 US engine at thetime of market launch in Autumn 2008.

1 - BMW 335d 2 - BMW X5 xDrive35d

Model

Modelseries

Engine

Cylindercapacityincm3

Bore/stroke

inmm

Powerin

kW/bhpatrpm

Torquein

Nmatrpm

Marketlaunc

h

335d E90 M57D30T2 2993 90/84200/265

4200580

175011/08

X5 xDrive35d E70 M57D30T2 2993 90/84200/265

4200580

175011/08


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5

M57D30O2 730d E65 2993 170/231 520 DDE626 3/05 9/08

M57D30O2 330d E90 2993 170/231 500 DDE626 9/05 9/08

M57D30O2 330d E91 2993 170/231 500 DDE626 9/05 9/08

M57D30O2 530d E61 2993 170/231 500 DDE626 9/05 in production


M57D30O2 730Ld E66 2993 170/231 520 DDE626 9/05 9/08

M57D30O2 X3 3.0d E53 2993 160/218 500 DDE626 9/05 in production

M57D30U2 325d E90 2497 145/197 400 DDE606 9/06 in production



M57D30T2 335d E90 2993 210/286 580 DDE626 9/06 in production



M57D30T2 X3 3.0sd E83 2993 210/286 580 DDE626 9/06 in productionM57D30U2 325d E92 2497 145/197 400 DDE606 3/07 in production




M57D30O2 X5 3.0d E70 2993 173/235 520 DDE626 3/07 in production





M57D30T2 635d E64 2993 210/286 580 DDE626 9/07 in productionM57D30T2 X5 3.0sd E70 2993 210/286 580 DDE626 9/07 in production

M57D30O2 X6xDrive30d

E71 2993 173/235 520 DDE626 5/08 in production

M57D30T2 X6xDrive35d

E71 2993 210/286 580 DDE626 5/08 in production

Engine

Model

Modelseries

Cylindercapacity

incm3

Poweroutput

in(kW/bhp)

Torque

inNm

Engine

management

Firstused

Lastused


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Introduction.Advanced Diesel.

A diesel engine for North America

Impressive power and performance as well asexemplary efficiency have contributed tomaking BMW diesel engines an attractive aswell as future-oriented drive technology. Thistechnology is now being made available todrivers in North America.

BMW is introducing this diesel technology tothe USA and Canada under the name "BMWAdvanced Diesel". The introduction is anintegral part of the EfficientDynamics

development strategy, which has become asynonym for extremely low CO2emissions -not surprising when considering its extremelylow fuel consumption. EfficientDynamics isnot solely an instrument for reducing fuelconsumption but rather it is designed as anintelligent entity with increased dynamics. Notwithout good reasontheM57D30T2 engine isreferred to as the world's most agile dieselengine.

History

In 1892, Rudolf Diesel applied for a patent forhis first self-igniting combustion engine.Initially, this large, slow-running engine wasintended for stationary operation only. Theintricate engine structure and complicatedinjection system meantproduction costs werehigh. The first simple diesel engines were notparticularly comfortable and powerful-revvingmachines. It was not possible to mistake thedistinctive sound of the harsh combustion

process in the diesel engine when cold (dieselknock). Compared to thespark ignitionengine,it offered a poorer power/weight ratio,acceleration characteristics and lower specificoutput.

"Miniaturization" could be realized only byimproving materials and the manufacturingprocess during the course of commercialvehicle production. Although the first dieselvehicle was presented as early as 1936, it wasnot before the 1970s that the diesel enginebecame accepted as a viable drive source.The breakthrough came in the 1980s when

thedieselengine wasfinally refined enough tobe a real alternative to the spark ignitionengine. At this time, in view of the improveddynamics and acoustics the decision was

made to introduce the diesel engine in seriesproduction vehicles at BMW.

1 - Rudolf Diesel and his engine


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1983

The M21D24 engine introduced for the firsttime in the E28 as the 524td featured anexhaust turbocharger and had a displacementof 2.4 litres. It was derived from the M20 6-cylinder petrol engine and developed 85 kW/115 bhp. Both engines could therefore bebuilt on the same production facilities.

At that time, the performance with a top speedof 180 km/h and acceleration from 0 to 100km/h in 13.5 seconds set new standards in thedynamics of diesel motor vehicles. The 524tdwas therefore given the nickname "Sportdiesel".

Thiswas the first dieselengineat BMW and,atthe same time, the last for a long time in theUS market.

1985

The M21 was also built as a naturally-aspirated diesel engine as from September1985, making it possible to offer a cost-effective "entry-level engine". This enginemade a name for itself in the 324d (E30) as thesmoothestrunning auto-ignitionengine on themarket.

1987

As the world's first carmaker to do so, BMWintroduced the electronic enginemanagement system, the so-called DigitalDiesel Electronics (DDE). Faster and moreexact than a mechanical control system, theelectronics effectively controls:

Exhaust emission characteristics

Fuel consumption characteristics

Noise emission

Engine running refinement.

2 - BMW 524td with M21 engine


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1991

1991 saw the debut of the newly developedM51D25 engine which, with intercooling andan output of 105 kW/143 bhp was the mostpowerful diesel engine in its class throughoutthe world. It replaced the M21 engine and was

fitted with a crankcase based on a completelynew design.

The engine was offered in the output variants115 bhp and 143 bhp. Exhaust emission andfull load smoke were reduced by a V-shapedmain combustion chamber in the piston.

1994

TheM41 enginewasthefirst 4-cylinder dieselenginetobe used atBMW. It was derived fromthe M51D25 engine and shared 56 % of itscomponents. New features included the

hollow-cast camshaft mounted in 5 bearingsas well as a cylinder head cover the isolatedstructure-borne noise.

This engine was fitted in various models of theE36 series.

3 - BMW 525tds with M51 engine


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1999

The first V8 diesel engine, the M67D40engine, with 4 litre displacement waspresented in the E38 which developed anoutput of 175 kW. BMW proved its technicalauthority with the, at that time, world's mostpowerful passenger vehicle dieselenginewith

common rail fuel injection and 2 exhaustturbochargers.

The engine is fitted with a crankcase madefrom high-strength cast iron with vermiculargraphite (GGV), an aluminium cylinder headand a two-piece oil sump.

2001

The M47TU with the second generationcommon rail injection system and DDE5boosted thepower output to 110 kW/150bhp.

TheM57D30 engine is a further developmentof the M51D25 engine. It has a cast ironcasing fitted with a light alloy cylinder headwith 4-valve technology. The M57 engine istheworld's first 6-cylinder in-line dieselenginein a passenger vehicle that is equipped with

future-oriented common rail injectiontechnology.

This new, highly complex electronicallycontrolled fuel injection system perfectlysatisfies the demands for high and constantinjection pressure over the entire injectionperiod. The engine offers substantially lowerfuel consumption compared to swirl-chamberengines, superior performance and smoothengine operation under extreme conditions.

6 - BMW 740d with M67 engine


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2004

The M57TU TOP engine with 2-stageturbocharging is introduced as the mostpowerful diesel engine (E60 and E61). Onesmall and one large turbocharger is used inthe2-stage turbocharging system. The diesel

engine in the 535d develops 40 kW/54 bhpmore than at the same displacement (3.0litres) in the 530d.

The power output is 200 kW/272 bhp. Themaximum torque of 560 Nm is reached at2000 rpm. With this extraordinary engine, LucAlphand won not only the diesel classificationof the Paris-Dakar Rally, but also came fourth

in the overall rankings.

7 - BMW 530d with M57 engine

8 - BMW X5 3.0d with M57TU TOP engine


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2005

The M57TU2 engine is fitted in the E65. Inaddition to the increase in output and torque,it boasts the following technical features:

Reduced weight through aluminiumcrankcase

3rd generation common rail system withpiezo-injector and a fuel rail pressure of1600 bar

Compliance with the exhaust emissionregulation EURO 4 and diesel particulatefilter as standard

Optimized electric boost pressure actuatorfor the turbocharger with variable turbinegeometry.

2005

The M67 engine in the E65 wascomprehensively reengineered in the sameyear. The aim was to achieve a distinct boostin dynamics by increasing power output andreducing weight. In the case of the M67specifically this aim is reflected in an increase

in power output of 16 % while simultaneouslyreducing the engine weight by 14 % - andachieved without increasing fuel consumption.

This was mainly achieved through a new,lightweight aluminium crankcase and byincreasing the displacement to 4.4 litres.

9 - BMW 730d with M57TU2 engine


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2006

In 2006, the M57TU TOP engine was re-engineered and equipped with the sametechnical details as the M57TU2, such as analuminium crankcase and piezo-fuel injectors.This engine was given the designation

M57D30T2. It was introduced simultaneouslyinto the 3 Series as the 335d and in the X3 as

the 3.0sd. This re-engineering resulted infurther-improved power characteristics,enhanced smooth operation and a significantreduction in fuel consumption. This engineforms the basis for re-introducing dieseltechnology into the USA after more than 20years.

10 - BMW 745d with M67TU engine

11 - X3 3.0sd with M57TU2 TOP engine


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Legislation

Since the first exhaust emission legislation forpetrol engines came into force in the mid-1960s in California, the permissible limits for arange of pollutants have been further andfurther reduced. In the meantime, all industrialnations have introduced exhaust emissionlegislation that defines the emission limits forpetrol and diesel engines as well as the testmethods.

Essentially, the following exhaust emission

legislation applies: CARB legislation (California Air Resources

Board), California

EPA legislation (Environmental ProtectionAgency), USA

EU legislation (European Union) andcorresponding ECE regulations (UNEconomic Commission for Europe), Europe

Japan legislation.

This legislationhas lead to thedevelopment ofdifferent requirements with regard to the

limitation of various components in theexhaust gas. Essentially, the following exhaustgas constituents are evaluated:

Carbon monoxide (CO)

Nitrogen oxides (NOx)

Hydrocarbons (HC)

Particulates (PM)

It can generally be said that traditionally more

emphasis is placed on low nitrogen oxideemissions in US legislation while in Europethefocus tends to be more on carbon monoxide.

The following graphic compares the standardapplicable to BMW diesel vehicles with thecurrent standards in Europe. Adirectcomparison, however, isnot possibleas

different measuring cycles are used and

different values are measured forhydrocarbons.


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Although the European and US standardscannot be compared 1:1 it is clear that

requirements relating to nitrogen oxideemissions are considerably more demanding.

Diesel engines generally have higher nitrogenoxide emission levels than petrol engines as

diesel engines are normally operated with anair surplus.

For this reason, the challenge of achievingapproval in all 50 states of the USA had to bemet with a series of new technologicaldevelopments.

12 - Comparison of exhaustemission legislation

Standard Valid from CO[mg/km]

NOx[mg/km]

HC + NOx*[mg/km]

NMHC**[mg/km]

PM[mg/km]

EURO 4 01.01.2005 500 250 300 - 25

EURO 5 01.09.2009 500 180 230 - 5

EURO 6 01.09.2014 500 80 170 - 5

LEV II MY 2005 2110 31 - 47 6

* In Europe, the sum of nitrogen oxide and hydrocarbons is evaluated, i.e. the higher the HCemissions, the lower the NOxmust be and vice versa.

** In the USA, only the methane-free hydrocarbons are evaluated, i.e. all hydrocarbons withno methane


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Overview of innovations, modifications and special features

The following table provides an overview ofthe special features of the M57D30T2 USengine. They are divided into variouscategories.

New development signifies a technologythat has not previously been used on BMWengines.

Modificationsignifies a component thatwasspecifically designed for the

M57D30T2 US engine but does notrepresent a technical innovation.

Adopted describes a component that hasalready been used in other BMW engines.

This Product Information describes only themain modifications to the M57D30T2 enginecompared to the Europe version as well asfundamental vehicle systems specific to dieselengines.

Component Newdevelopment

Modification

Adopted

Remarks

Engine mechanical system 7 Very few modifications have been made tothe basic engine. The modifications thathave been made focus mainly on ensuring

smooth engine operation.A significant feature, however, is the OBDmonitoring of the crankcase breather.

Air intake and exhaustsystem

7 The most extensive changes were made tothe air intake and exhaust system. Forinstance, low pressure exhaust gasrecirculation (low pressure EGR) is used forthe first time at BMW on the E70.

In addition to other minor adaptations, thereare substantial differences in the sensor andactuator systems.

Cooling system 7 In principle, the cooling system corresponds

to that of the Europe versions, however, ithas been adapted to hot climaterequirements.

Fuel preparation system 7 The functional principle of the fuelpreparation system does not differ from thatof the Europe version, however, individualcomponents have been adapted to thedifferent fuel specification.


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Component Newdevelopment

Modification

Adopted

Remarks

Fuel supply system 7 The fuel supply system is vehicle-specificand corresponds to the Europe version.Thereare,however,significant differences topetrol engine vehicles.

SCR system(Selective CatalyticReduction)

7 The SCR system is used for the first time atBMW. Nitrogen oxide emissions aredrastically reduced by the use of a reducingagent that is injected into theexhaust systemupstream of a special SCR catalyticconverter. Since the reducing agent iscarried in the vehicle, a supply facility, madeup of two reservoirs, is part of this system.

Engine electrical system 7 The engine is equipped with the new DDE7(digitaldiesel electronics) control unit thatwillbe used in thenext generation dieselengines(N47, N57).

The preheater system also corresponds tothe N47/N57 engines.

Automatic transmission 7 The automatic transmission corresponds tothat in the ECE variant of the X5 xDrive35d.The gearbox itself has already been used inthe US version of the X5 4.8i, however, adifferent torque converter is used for thediesel model.


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Technical data

Thefollowing table compares the M57D30T2US engine with petrol engines that are offeredfor the same models.Designation N52B30O1 N54B30O0 N62B48O1 M57D30T2

Type Straight 6 Straight 6 V8 Straight 6

Displacement [cm3] 2996 2979 4799 2993

Firing order 1-5-3-6-2-4 1-5-3-6-2-4 1-5-4-8-6-3-7-2 1-5-3-6-2-4

Stroke/bore [mm] 88.0/85 88.9/84 88.3/93 90.0/84

Output

at engine speed

[kW/hp*]

[rpm]

193/260

6600

225/300

5800

261/350

6250

200/265

4200Torqueat engine speed

[Nm/lbft][rpm]

305/2252500

407/3001400

475/3503500

580/4281750

Governed enginespeed limit

[rpm] 7000 7000 6500 4800

Power output perlitre

[hp/l] 86.7 100 72.9 89.3

Compression ratio 10.7 10.2 10.5 16.5

Cylinder spacing [mm] 91 91 98 91

Valves/cylinder 4 4 4 4

Intake valve [mm] 34.2 31.4 35.0 27.4

Exhaust valve [mm] 29.0 28.0 29.0 25.9

Main bearingjournaloncrankshaft

[mm] 56 56 70 60

Big-end bearingjournaloncrankshaft

[mm] 50 50 54 45

Fuel specification [RON] 98 98 98

Fuel [RON] 91-98 91-98 91-98 Diesel

Enginemanagement

MSV80 MSD80 ME9.2.3 DDE7.3

Exhaust emissionstandard US

ULEVII ULEVII ULEVII LEVII

* SAE-hp


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Full load diagrams

To get an idea of the performance of theM57D30T2 US engine, it is compared to

various petrol engines in the following full loaddiagrams.

By comparing these two 3 litre engines it canbe clearly seen that, despite virtually identical

power output, the maximum torque of thediesel is almost double as high.

13 - M57D30T2 US enginecompared toN52B30O1 engine


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This enormous difference in maximum torqueis also apparent when comparing the

turbocharged 3 litre petrol engine that has aconsiderably higher nominal power output.



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Even the 4.8 litre V8 engine cannot achievethe maximum torque of the 3 litre dieselengine.

However, the decisive factor is the low enginespeeds at which the diesel engine develops

this high torque. This means that more poweris available in this range. In terms of poweroutput, the diesel engine is superior to any ofthese petrol engines up to an engine speed of4000 rpm.



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System components.Advanced Diesel.

Engine mechanical system

Only slight modifications have been made tothe engine mechanical system compared tothe Europe version.

The modifications include:

Crankcase

Crankshaft and big-end bearings

Pistons

Crankcase breather.

Crankshaft and big-end bearings

Only lead-free crankcase and big-endbearings are used in the M57D30T2 USengine. This conforms to requirements

relating to environmental protection and thedisposal of end-of-life vehicles.

Crankcase

In contrast to the Europe version, theM57D30T2 US engine has a largerreinforcement panel on the underside of thecrankcase.

The reinforcement panel now covers four ofthe main bearing blocks for the crankshaft.

In principle, the reinforcement panel serves toenhance the stability of the crankcase.However, the enlargement was realized solelyfor acoustic reasons.

3 Never drive the vehicle without thereinforcement panel.1

Pistons

The piston pin has a greater offset than in theEurope version. The offset of the piston pinmeans that the piston pin is slightly off centre.This provides acoustic advantages during

changes in piston contact. The acousticadvantages of increasing the offset are furtherdeveloped particularly at idle speed.


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Crankcase breather

The crankcase breather in the US version isgenerally heated. In addition, operation of thecrankcase breather is OBD monitored (OnBoard Diagnosis). This is because a leakingsystem would produce emissions.

The only probable reason for a leak in thesystem would be that the blow-by pipe is notconnected to the cylinder head cover. Tofacilitate protection of this situation by theOBD, the heating line is routed via a connectorto the cylinder head cover (2). Essentially, thisconnector serves only as a bridge so thatactuation of the heating system is loopedthrough. The plug connection is designed insuch a way that correct contact is made onlywhen the blow-by pipe has been connected

correctly to the cylinder head cover, i.e. thecontact for the heating system is not closed ifthe blow-by pipe is not connected to thecylinder head cover. OBD recognizes thissituation as a fault.

3 If the blow-by pipe is not connected to thecylinder head correctly, the OBD will activatethe MIL (Malfunction Indicator Lamp).1

1 - Blow-by pipe

Index Explanation

1 Cylinder head cover

2 Blow-by heater connector for OBDmonitoring

3 Blow-by heater connector at wiringharness

4 Filtered air pipe5 Intake air from intake silencer

6 Blow-by heater connector at blow-by pipe

7 Intake air to exhaust turbocharger

8 Blow-by pipe


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Air intake and exhaust system

The M57D30T2 US engine exhibits thefollowing special features in the air intake andexhaust system:

Electric swirl flaps

Electric exhaust gas recirculation valve(EGR valve)

Low pressure EGR

Turbo assembly adapted for low pressureEGR.

2 - Air intake and exhaust system - M57D30T2 US engine


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Index Explanation Index Explanation

1 M57D30T2 US engine 18 Oxidation catalytic converter anddiesel particulate filter

2 Intake silencer 19 Exhaust gas temperature sensorbefore oxidation catalytic converter

3 Hot-film air mass meter (HFM) 20 Oxygen sensor

4 Compressor bypass valve 21 Wastegate

5 Exhaust turbocharger, low pressurestage

22 Turbine control valve

6 Exhaust turbocharger, high pressurestage

23 Exhaust pressure sensor afterexhaust manifold

7 Bypass valve for high pressure EGRcooler

24 Swirl flap regulator

8 High pressure EGR cooler 25 Boost pressure sensor

9 Temperature sensor, high pressureEGR

26 Exhaust differential pressure sensor

10 High pressure EGR valve 27 NOxsensor before SCR catalyticconverter

11 Throttle valve 28 Temperature sensor after dieselparticulate filter

12 Charge air temperature sensor 29 Metering module (for SCR)

13 Intercooler 30 Mixer (for SCR)

14 Low pressure EGR valve withpositional feedback

31 SCR catalytic converter

15 Temperature sensor,low pressure EGR

32 NOxsensor after SCR catalyticconverter

16 Low pressure EGR cooler 33 Digital Diesel Electronics (DDE)

17 Exhaust gas temperature sensorafter oxidation catalytic converter

34 Rear silencer


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Air intake system

Intake air system

The intake air system differs on the E70 andE90. Both vehicles draw in unfiltered airbehind the BMW kidney grille.

On the E90, the intake silencer is located atthefrontright of theenginecompartmentfixed

to the vehicle. On the E70, the intake silenceris fixed over the engine.

3 - Air intake system E70 and E90


A Air intake system E70 3 Intake silencer (air cleaner housing)

B Air intake system E90 4 Hot-film air mass meter (HFM)

1 Intake 5 Filtered air pipe

2 Unfiltered air pipe 6 Blow-by pipe


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Swirl flaps

The engine is equipped with the familiar swirlflaps in thetangential port. A special feature on

the US engine is the electric actuating systemwith positional feedback.

This system provides advantages in terms ofcontrol, however, it is also a prerequisite formeeting OBD requirements.

4 - Intake manifold with electric swirl flaps


1 Linkage for operating the swirl flaps 5 Swirl port

2 Connection to throttle valve 6 Tangential port

3 Intake manifold 7 Swirl flaps

4 Electric motor


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Exhaust system

5 - E70 and E90 exhaust systems


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A Exhaust system E70 6 SCR catalytic converter

B Exhaust system E90 7 NOxsensor after SCR catalyticconverter

1 Oxygen sensor and concealedexhaust temperature sensor beforeoxidation catalytic converter

8 Rear silencer

2 Exhaust gas temperature sensorafter oxidation catalytic converter

9 Exhaust gas temperature sensorafter diesel particulate filter

3 Differential pressure sensor 10 Metering module

4 NOxsensor before SCR catalytic

converter

11 Diesel particulate filter

5 Mixer


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Exhaust gas recirculation (EGR)

Exhaust gas recirculation is one of theavailable options for reducing NOxemissions.Adding exhaust gas to the intake air reducesthe oxygen in the combustion chamber, thusresulting in a lower combustion temperature.

The EGR systems in the E70 and E90 differ.Both vehicles are equipped with the familiarEGR system. Due to its higher weight, the E70additionally features low pressure EGR, usedfor the first time at BMW.

Low pressure EGR

The known EGR system has been expandedby the low pressure EGR on the E70. Thissystem offers advantages particularly at highloads and engine speeds. This is why it is used

in the heavier E70 as it is often driven in thehigher load ranges.

The advantage is based on the fact that ahigher total mass of exhaust gas can berecirculated. This is made possible for tworeasons:

Lower exhaust gas temperature

The exhaust gas for the low pressure EGRis tapped off at a point where a lower

temperature prevails than in the highpressure EGR. Consequently, the exhaustgas has a higher density thus enabling ahigher mass.

In addition, the exhaust gas is added to thefresh intake air before the exhaustturbocharger, i.e. before the intercooler,where it is further cooled. The lowertemperature of the total gas enables ahigher EGR rate without raising thetemperature in the combustion chamber.

Recirculation before the exhaustturbocharger

Unlike in the high pressure EGR where theexhaust gas is fed to the charge air alreadycompressed, in this systemtheexhaust gasis added to the intake air before the exhaustturbocharger. A lower pressure prevails inthis area under all operating conditions.This makes it possible to recirculate a largevolume of exhaust gas even at higherengine speed and load whereas this islimited by the boost pressure in the highpressure EGR.

6 - Low pressure EGR


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Thefollowing graphic shows thecontrol of theEGR system with low pressure EGR:

As already mentioned, the low pressure EGRhasthegreatestadvantage at higher loadsandis therefore activated, as a function of thecharacteristic map, only in this operatingmode. The low pressure EGR, however, isnever active on its own but rather alwaysoperates together with thehigh pressure EGR.

Added to this, it is only activated at a coolanttemperature of more than 55 C. The lowpressure EGR valve is closed as from a certainload level so that only the high pressure EGRvalve is active again. This means the EGR rateis continuously reduced.

7 - Control of EGR system


1 No exhaust gas recirculation 3 High and low pressure EGR areactive

2 Only high pressure EGR is active


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The low pressure EGR system is located onthe right-hand side on the engine directly nextto the diesel particulate filter and the lowpressure stage of the turbo assembly. The

exhaust gas is branched off directly after thediesel particulate filter and fed to the intake airbefore the compressor for the low pressurestage.

8 - Installation position LP EGR


1 Diesel particulate filter 4 Low pressure EGR

2 Turbo assembly 5 Exhaust system

3 Exhaust turbocharger, low pressurestage


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9 - Low pressure EGR intake


1 Low pressure EGR valve 3 Low pressure EGR port

2 Compressor, low pressure stage 4 Unfiltered air intake


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The following graphic shows the componentsof the low pressure EGR:

There is a fine meshed metal screen filterlocated at the exhaust gas inlet from the dieselparticulate filter to the low pressure EGRsystem. The purpose of this filter is to ensurethat no particles of the coating particularly in anew diesel particulate filter can enter the lowpressure EGR system. Such particles would

adversely affect the compressor blades of theexhaust turbocharger.

3 The metal screen filter must be installedwhen fitting the low pressure EGR cooler tothe diesel particulate filter otherwise there is arisk of the turbocharger being damaged.1

10 - LP EGR components


1 Temperature sensor,

low pressure EGR

5 Coolant infeed

2 Low pressure EGR valve 6 Coolant return

3 Connection for positional feedback 7 Low pressure EGR cooler

4 Vacuum unit forlow pressure EGR valve

8 Sheet metal gasket with filter


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High pressure EGR Theexhaust gas recirculation known to date isreferred to here as the high pressure EGR inorder to differentiate it from the low pressureEGR.

Compared to the Europe version, the highpressure EGR is equipped with the followingspecial features:

Electric EGR valve with positional feedback

Temperature sensor before high pressureEGR valve

EGR cooler with bypass.11 - High pressure EGR

12 - High pressure EGR system


1 Coolant infeed 5 High pressure EGR cooler

2 High pressure EGR valve 6 Vacuum unit of bypass valve for highpressure EGR cooler

3 Throttle valve 7 Coolant return

4 Temperature sensor, high pressureEGR


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Cooling system

Thecooling system, is in part, vehicle-specific.In principle, there are scarcely any differencesbetween the cooling systems on petrol anddiesel engines.

The two basic differences compared to petrolengines are:

No characteristic map thermostat

EGR cooler.

The E70 and E90 differwithregard tothe EGRcooler. Since the E70 is equipped with a lowpressure EGR system, it has a second EGRcooler, the low pressure EGR cooler.


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13 - X5 xDrive35d cooling system


1 RadiatorCoolant-to-air heat exchanger

10 Heating heat exchanger

2 Gearbox coolerCoolant-to-air heat exchanger

11 Duo-valve

3 Electric fan 12 Auxiliary coolant pump4 Thermostat, gearbox oil cooler 13 Engine oil cooler

Engine oil-to-coolant heat exchanger

5 High pressure EGR cooler 14 Expansion tank

6 Thermostat 15 Gearbox oil coolerGearbox oil-to-coolant heatexchanger

7 Coolant pump 16 Ventilation line

8 Low pressure EGR cooler 17 Additional radiatorCoolant-to-air heat exchanger

9 Coolant temperature sensor


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14 - 335d cooling system


1 Gearbox coolerCoolant-to-air heat exchanger

9 Heating heat exchanger

2 RadiatorCoolant-to-air heat exchanger

10 Duo-valve

3 Additional radiatorCoolant-to-air heat exchanger

11 Auxiliary coolant pump

4 Thermostat, gearbox oil cooler 12 Engine oil coolerEngine oil-to-coolant heat exchanger

5 High pressure EGR cooler 13 Expansion tank

6 Thermostat 14 Gearbox oil coolerGearbox oil-to-coolant heatexchanger

7 Coolant pump 15 Ventilation line

8 Coolant temperature sensor 16 Electric fan


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The fuel preparation system differs neither interms of design layout nor function from theEurope version. However, some componentshave been adapted to the different fuelspecification.

These components are: High-pressure pump

Fuel rail

Fuel injectors.

These adaptations are restricted to differentcoatings and materials on the inside.


A Fuel feed 6 Return line

B Fuel return 7 Feed line

C Fuel high pressure 8 Fuel temperature sensor

1 Fuel rail pressure sensor 9 High-pressure line

2 High-pressure line 10 Fuel rail

3 Leakage oil line 11 Restrictor

4 Piezo injector 12 High-pressure pump

5 Fuel rail pressure control valve 13 Volume control valve


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Overview of fuel supply system

16 - E90 Diesel fuel supply system


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Design

As for petrol engines, the fuel system isvehicle-specific. There are, however, severalgeneral and significant differences compared

to petrol engine vehicles.

These are:

The system includes a fuel return line

The breather system is significantly simpler There is no carbon canister (AKF) and no

fuel tank leakage diagnosis module (DMTL)

There is no pressure regulator

The fuel filter is not located in the fuel tank.

The design layout of the fuel supply systemsin the E70 and E90 are described in thefollowing.


1 Fuel filler neck 5 Right-hand service opening

2 Left-hand service opening 6 Filler vent

3 Fuel return line 7 Electric fuel pump controller

4 Fuel filter with heating system


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E70 with diesel engine

In addition to delivering the fuel to the engine,the fuel supply systemalso filters the fuel. Thefuel tank contains an additional ventingsystem.

The fuel tank is divided into two chambersbecause of the space available in the vehicle.The fuel supply system has two delivery units

that are accommodated in the right and leftfuel tank halves.

The fuel pump (3) with intake filter (2) is a partof the right-hand delivery unit. The surgechamber including a suction jet pump (10)with pressure relief valve (11) and initial fillvalve (1) as well as a lever-type sensor (G)complete this delivery unit.

17 - Fuel tank on E70 with diesel engine


A Fuel filler cap 1 Initial fill valve

B Pressure relief valve 2 Intake mesh filter

C Non-return valve 3 Fuel pump

D Surge chamber 4 Pressure relief valve

E Fuel tank 5 Feed line

F Service cap 6 Return line

G Lever-type sensor 7 Leak prevention valve

H Filler vent valve 8 Suction jet pump

I Connection 9 Air inlet valve

J Maximum fill level 10 Suction jet pump

K Non-return valve 11 Pressure relief valveL Filter


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The suction jet pump (8), lever-type sensor(G), leak prevention valve (7) and air inlet valve(9) belong to the left-hand delivery unit.

A line leads from the filler vent valve (H) to thefilter (L). The fuel filler pipe is connected to thisline via the non-return valve (K).

E90 with diesel engine

18 - Fuel tank on E90 with diesel engine


A Fuel filler cap 1 Initial fill valve

B Pressure relief valve 2 Intake mesh filter

C Non-return valve 3 Fuel pump

D Surge chamber 4 Pressure relief valve

E Fuel tank 5 Feed line

F Service cap 6 Return lineG Lever-type sensor 7 Leak prevention valve

H Filler vent valve 8 Suction jet pump

I Connection 9 Non-return valve

J Maximum fill level 10 Suction jet pump

L Filter 11 Pressure relief valve


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Functions of the fuel supply system

Fuel tank

A pressure relief valve (B) is integrated in thefuel filler cap (A) to protect the fuel tank (E)from excess pressure. A non-return flap (C) islocated at the end of the fuel filler neck. Thenon-return flap prevents thefuel from sloshingback into the fuel filler neck.

The components in the fuel tank can bereached via the two service caps (F).

The fuel fill level can be determined via the twolever-type sensors (G).

The surge chamber (D) ensures that the fuelpump always has enough fuel available for

delivery.

19 - Fuel tank for E70 with diesel engine


A Fuel filler cap E Fuel tank

B Pressure relief valve F Service cap

C Non-return valve G Lever-type sensor

D Surge chamber


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In the event of the surge chamber beingcompletely empty, the initial filling valve (1)ensures that fuel enters the surge chamberwhile refuelling.

The fuel reaches the fuel pump (3) via theintake filter (2), then continues through thedelivery line (5) to the fuel filter. The fuel pumpis located in the surge chamber. A pressurerelief valve (4) is integrated in the fuel pump toprevent pressure in thedelivery line from risingtoo high. As the engine switches off, thedelivery line is depressurized but cannot rundry because, provided the system is not

leaking, no air is able to enter it. In addition,after the fuel pump has switched off, the fuelpressure/temperature sensor is checked forplausibility.

Fuel that is required for lubrication and thefunction of high pressure generation flowsback into the fuel tank via the return line (7).The fuel coming from the return line is dividedinto two lines downstream of the leakprevention valve (7). The non-return valveprevents the fuel tank from draining in theevent of damage to lines on the engine or

underbody. It also prevents the return linefrom running dry while the engine is off.

One of the lines guides the fuel into the surgechamber via a suction jet pump (10). Thesuction jet pump transports the fuel from thefuel tank into the surge chamber. If the fueldelivery pressure in the return line increasestoo much, the pressure relief valve (11) opensand allows the fuel to flow directly into thesurge chamber.

An air inlet valve is used in the E70. The airinlet valve (9) ensures that air can enter the line

when the engine is off, preventing fuel fromflowing back from the right-hand half of thefuel tank to the left.

Instead of the air inlet valve (9) a non-returnvalve is used on the E90. The non-return valveensures that, while the engine is off, fuel fromthe right-hand half of the fuel tank cannot flowback into the left-hand half. The return systemremains completely filled with fuel.

A further line branches off into the left-handhalf of the fuel tank after the non-return valve(7) and transports the fuel into the surgechamber via the suction jet pump (8).


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Components of the fuel supply system

Pressure relief valve in fuel filler cap

The pressure relief valve ensures that, if thereis a problem with fuel tank ventilation, anyexcess pressure that may form can escapeand the fuel tank is not damaged.

If excess pressure forms in the fuel tank, thiscauses the valve head (1) and with it the entirepressure relief valve (5) to be lifted off thesealed housing (6). The excess pressure cannow escape into the atmosphere. The excesspressure spring (2) determines the openingpressure. The excess pressure spring uses a

defined pressure to push the pressure reliefvalve onto the sealed housing and issupported by the brace (3).

22 - Pressure relief valve

Index Explanation

1 Valve head

2 Excess pressure spring

3 Brace

4 Bottom section of housing

5 Pressure relief valve

6 Sealed housing


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Protection against incorrect refuelling

23 - Protection againstincorrect refuelling


1 Housing 5 Torsion spring

2 Locking lever 6 Rivet

3 Tension spring 7 Hinged lever

4 Flap 8 Ground strap

24 - Protection against

incorrect refuelling


21 mm Petrol fuel nozzle 24 mm Diesel fuel nozzle


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The protection against incorrect refuellingfeature ensures that the fuel tank cannot befilled with gasoline. As the previous graphicshows, only a fuel nozzle with a diameter ofapproximately 24 mm can fit. If the diameter isapproximately 21 mm, the flap (4) does notopen as the hinged lever (7) and the lockinglever (2) cannot be pushed apart.

If a diesel fuel nozzle is inserted, this pushesthe locking lever (2) and the hinged lever (7) at

the same time. The hinged lever is pushedoutwards against the tension spring (3) andreleases the flap (4). This is only possible,however, if the hinged lever cannot movefreely and is also locked in position by the fuelnozzle.

3 To open the protection against incorrectrefuelling feature in the workshop, a specialtool is required.1


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Fuel pump

Today's diesel vehicles are fitted with electricfuel pumps only. The electric fuel pump isdesigned to deliver a sufficient amount of fuelto lubricate and cool the injectors and thehigh-pressure pump and to satisfy themaximum fuel consumption of the engine. Ithas to deliver the fuel at a defined pressure.That means that when the engine is idling orrunning at medium power, the fuel pump

delivers several times more than the amountof fuel required. The fuel pump deliversapproximately three or four times the volumeof maximum possible fuel consumption.

The electric fuel pump is located in the fueltank. There it is well protected againstcorrosion and the pump noise is adequatelysoundproofed.

25 - Electric fuel pump


1 Impeller 6 Electrical connection

2 Drive shaft 7 Sliding contacts

3 Electric motor 8 Pressure chamber

4 Pressure relief valve 9 Intake section

5 Pressure connection


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The fuel pump on BMW diesel engines mayeither be a gear pump, a roller-cell pump or ascrew-spindle pump. The following fuelpumps are used on USA vehicles:

The operating principle of each of these typesofpump is described below. The pump itself isdriven by the drive shaft (2) of the electricmotor (3). The electric motor is controlled by

the electrical connection (6) and slidingcontacts (7).

Passing first through the intake filter and thentheremainderof the intakesection (9), the fuelenters the impeller (1). The fuel is pumpedthrough pressure chamber (8) on the electricmotor, past the pressure connection (5) andonwards to the fuel filter and engine.

If the fuel delivery pressure increases to animpermissible value, the pressure relief valve(4) opens and allows the fuel to flow into thesurge chamber.

Control

In principle, there are three different types offuel pump control:

Unregulated:The fuel pump operates with "ignition ON".If the engine is not started, the fuel pumpswitches off again after a defined period. Ifthe engine is running, the fuel pump

operates at maximum output and speed.The fuel is switched off with "engine OFF".

Speed-regulated:The fuel pump operates with "ignition ON".If the engine is not started, the fuel pumpswitches off again after a defined period.The fuel pump is controlled by aninterposed control unit (fuel pumpcontroller) in response to a request signalfrom the DDE. The fuel pump controllermonitors and regulates the pump speed. Ifthe engine is switched off, so too is the fuelpump.

Pressure-regulated:The fuel pump operates with "ignition ON".If the engine is not started, the fuel isswitched off at a specific pressure. Whenthe engine is running, the fuel pump isregulated on-demand by the interposedfuel pump controller in response to a loadsignal from the DDE in order to ensure auniform fuel pressure at the inlet to thehigh-pressure pump.

Bothspeed regulation and pressure regulationhave improved fuel economy, although it has

been possible to improve fuel economyfurther still with pressure regulation. Otherpositive side effects include an increase in thefuel pump's service life, an unloading of thevehicle electrical system and a reduction infuel pump noise.

Vehicle Fuel pump

E70 Screw-spindle pump

E90 Gear pump

Vehicle Control

E70 Pressure control

E90 Speed control


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Gear pump

The type of gear pump used is a rotor pump.

The rotor pump comprises an outer rotor (1)with teeth on the inside, and an inner rotor (4)with teeth on the outside. The inner rotor isdriven by the drive shaft (5) of the electricmotor. The outer rotor is propelled by theteeth of the inner rotor and thus turns insidethe pump housing.

The inner rotor has one tooth fewer than theouter rotor, which means that, with eachrevolution, fuel is carried into the next tooth

gap of the outer rotor.

During the rotary motion, the spaces on theintake side enlarge, while those on thepressure side become proportionatelysmaller.

The fuel is fed into the rotor pump through twogrooves in the housing, one on the intake sideand one on the pressure side. Together withthe tooth gaps, these grooves form the intakesection (6) and pressure section (3).

26 - Gear pump/rotor pump

Index Explanation

1 Outer rotor

2 Fuel delivery to the engine

3 Pressure section

4 Inner rotor

5 Drive shaft

6 Intake section

7 Fuel from the fuel tank


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Screw-spindle pump

With the screw-spindle pump, two screwspindles intermesh in such a way that theflanks form a seal with each other and thehousing. In the displacement chambersbetween the housing and the spindles, thefuel is pushed towards the pressure side withpractically no pulsation.

In this way, the screw spindles pump fuelawayfrom the fuel tank (5). The fuel is then fed tothe engine (3) through the pump housing andthe fuel delivery line.

27 - Screw-spindle pump

Index Explanation

1 Drive shaft screw spindle

2 Gearwheel

3 Fuel delivery to the engine

4 Screw spindle

5 Fuel from the fuel tank


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Fuel filter

The fuel filter with heater illustrated here wasused in vehicle models with diesel engine anddistributor injection pump. Later models withdiesel engine and common rail system areequipped with the following fuel filters.

3 BMW recommends the use of parts andaccessories for the vehicle that have beenapproved by BMW for this purpose. Theseparts and accessories have been tested byBMW for their functional safety andcompatibility in BMW vehicles. BMW acceptsproduct responsibility for them. However,BMW cannot accept any liability for non-approved parts or accessories.1

The job of the fuel filter is to protect the fuel

system against dirt contamination. The high-pressure pump and injectors in particular arevery sensitive and can be damaged by eventhe tiniest amounts of dirt. The fuel deliveredto the engine is always fed through the fuelfilter. Contaminants are trapped by a paper-like material. The fuel filter is subject to areplacement interval.

28 - Fuel filter with heater (later vehicle models)

Index Explanation

1 Fuel filter heater connection

2 Inlet into the fuel filter heating

3 Locking clamp4 Fuel filter

5 Connection between fuel line andhigh-pressure pump


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Fuel filter heater

The fuel filter heater is attached to the fuelfilter housing and fixed with a locking clamp.The fuel flows through the fuel filter heatinginto the fuel filter.

Since winter-grade diesel fuel remains thineven at low temperatures, the fuel filter heateris not normally active when winter-gradediesel fuel is used. In order to save energy, thefuel filter heater is only switched on when thediesel actually becomes viscous due to low

temperatures.There are two different control systemsdepending on whether the fuel supply systemis speed-controlled or pressure-controlled.

Speed-controlled system

The fuel filter heater isnotcontrolled by theDDE. A pressure switch and a temperaturesensor are located in the fuel filter housing.

The fuel filter heater is switched on when bothof the following conditions are fulfilled:

Temperature drops below a defined value

A defined fuel delivery pressure isexceeded due to cold, viscous fuel.

If thefilter is clogged, a corresponding signal issent via a diagnosis line to the DDE. This is thecase when, despite a sufficiently hightemperature, the fuel pressure upstream ofthe filter does not drop.

Pressure-controlled system

The fuel filter heater is actuated by the DDE. Acombined fuel pressure and temperaturesensor upstream of the high pressure pump is

used.The fuel filter heater is switched on when bothof the following conditions are fulfilled:

Temperature drops below a defined value

The required fuel pressure is not reacheddespite increased power intake of theelectric fuel pump.

The DDE recognizes a clogged filter when thetarget pressure upstream of the high pressurepump is not reached despite a sufficientlyhighfuel temperature and high power intake of theelectric fuel pump.


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Overview of selective catalytic reduction

Selective catalytic reduction is a system forreducing nitrogen oxides (NOx) in the exhaustgas. For this purpose, a reducing agent (urea-water solution) is injected into exhaust gasdownstream of the diesel particulate filter.

The nitrogen oxide reduction reaction thentakes place in the SCR catalytic converter.

The urea-water solution is carried in tworeservoirs in the vehicle. The quantity ismeasured out such that it is sufficient for oneoil change interval.

The following graphic shows a simplifiedrepresentationof the system:

29 - Simplified representation of SCR system


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The reason for using two reservoirs is that theurea-water solution freezes at a temperatureof-11C. For this reason, thesmaller reservoiris heated but the larger reservoir not. In thisway, the entire volume of the urea-watersolution need not be heated, thus savingenergy. The amount is sufficient, however, tocover large distances.

The small, heated reservoir is referred to asthe active reservoir. A pump conveys the urea-water solution from this reservoir to themetering module. This line is also heated.

The larger, unheated reservoir is the passivereservoir. A pump regularly transfers the urea-water solution from the passive reservoir tothe active reservoir.


1 Passive reservoir 10 Pump

2 Level sensors 11 Filter

3 Filler pipe, passive reservoir 12 Transfer line

4 Metering line 13 Metering module

5 Metering line heater 14 Level sensor

6 Pump 15 Filler pipe, active reservoir

7 Function unit 16 Exhaust system

8 Heater in active reservoir 17 SCR catalytic converter

9 Active reservoir


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On the E70, the active reservoir, including thedelivery unit, is located on the right-hand sidedirectly behind the front bumper panel. Thepassive reservoir is located on the left in the

underbody, approximately under the driver'sseat. The transfer unit is installed on the rightin the underbody. Both fillers are located in theengine compartment.


1 Active reservoir 8 Passive reservoir

2 Delivery module 9 Metering module

3 Filler for active reservoir 10 Exhaust gas temperature sensorafter diesel particulate filter

4 Transfer unit 11 NOxsensor before SCR catalyticconverter

5 Filter 12 Filler for passive reservoir

6 SCR catalytic converter 13 Oxidation catalytic converter anddiesel particulate filter

7 NOxsensor after SCR catalytic

converter


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Installation locations in the E90

31 - Installations locations, E90 SCR system


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Onthe E90,both the active reservoir aswell asthe passive reservoir are located under theluggage compartment floor with the activereservoir being the lowermost of both. Thefillers are located on the left-hand side behindthe rear wheel where they are accessible

through an opening in the bumper panel. Thefillers are arranged in the same way as thereservoirs, i.e. the lowermost is the filler for theactive reservoir. The transfer unit and the filterare located behind the filler.


1 Active reservoir 8 Passive reservoir

2 Delivery module 9 Metering module

3 Filler for active reservoir 10 Exhaust gas temperature sensorafter diesel particulate filter

4 Transfer unit 11 NOxsensor before SCR catalyticconverter

5 Filter 12 Filler for passive reservoir

6 SCR catalytic converter 13 Oxidation catalytic converter anddiesel particulate filter

7 NOxsensor after SCR catalytic

converter


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Detailed system overview

32 - SCR system overview


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1 Operating vent 19 Filter

2 Passive reservoir 20 Metering line heater

3 Level sensors 21 Metering line

4 Filler vent 22 Operating vent

5 Filler pipe 23 Temperature sensor

6 Transfer line 24 Level sensor

7 Delivery module 25 Intake line heater

8 Delivery module heater 26 Filter

9 Delivery pump 27 Active reservoir

10 Reversing valve 28 Heating element in function unit

11 Filter 29 Function unit

12 Pressure sensor 30 Filler pipe

13 Filter 31 Metering module

14 Restrictor 32 NOxsensor before SCR catalyticconverter

15 Extractor connections 33 Exhaust gas temperature sensorafter diesel particulate filter

16 Filler vent 34 SCR catalytic converter

17 Non-return valve 35 NOxsensor after SCR catalytic

converter18 Transfer pump


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E90 System circuit diagram

34 - E90 SCR system circuit diagram


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1 DDE main relay 11 Transfer pump

2 Digital Diesel Electronics (DDE) 12 Evaluator, level sensor in activereservoir

3 SCR relay 13 Function unit with level sensor inactive reservoir, temperature sensorand heater

4 Power distributor, junction box 14 Active reservoir

5 Exhaust gas temperature sensorafter diesel particulate filter

15 Delivery module with delivery pump,reversing valve, pressure sensor andheater

6 Metering module 16 Heater module7 Power distributor, battery 17 NOxsensor after SCR catalytic

converter

8 Passive reservoir 18 NOxsensor before SCR catalyticconverter

9 Level sensors in passive reservoir 19 SCR load relay

10 Evaluator, level sensors in passivereservoir

20 Metering line heater


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Functions of selective catalytic reduction system

Selective catalytic reduction is currently themost effective system for reducing nitrogenoxides (NOx). During operation, it achieves anefficiency of almost 100 % and approx. 90 %over the entire vehicle operating range. Thedifference is attributed to the time the system

requires until it is fully operative after a coldstart.

This system carries a reducing agent, urea-water solution, in the vehicle.

The urea-water solution is injected into theexhaust pipe by the metering moduleupstream of the SCR catalytic converter. TheDDE calculates the quantity that needs to beinjected. The nitrogen oxide content in theexhaust gas is determined by the NOx sensorbefore the SCR catalytic converter.Corresponding to this value, theexact quantityof the urea-water solution required to fullyreduce the nitrogen oxides is injected.

The urea-water solution converts to ammoniain the exhaust pipe. In the SCR catalyticconverter, the ammonia reacts with the

nitrogen oxides to produce nitrogen (N2) andwater (H2O).

A further NOxsensor that monitors thisfunction is located downstream of the SCRcatalytic converter.

A temperature sensor in the exhaust pipe afterthe diesel particulate filter (i.e. before the SCRcatalytic converter) and the metering modulealso influences this function. This is becauseinjection of the urea-water solution onlybegins at a minimum temperature of 200 C.

35 - SCR functions


1 NOx sensor before SCR catalyticconverter 3 NOx sensor after SCR catalyticconverter

2 Metering module 4 Temperature sensor after dieselparticulate filter


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Chemical reaction

The task of the SCR system is to substantiallyreduce the nitrogen oxides (NOx) in theexhaust gas. Nitrogen oxides occur in twodifferent forms:

Nitrogen monoxide (NO)

Nitrogen dioxide (NO2).

Ammonia (NH3) is used for the purpose ofreducing the nitrogen oxides in a specialcatalytic converter.

The ammonia is supplied in the form of a urea-water solution.

The urea-water solution is injected by themetering system into the exhaust systemdownstream of thedieselparticulate filter. Therequired quantity must be metered exactly asotherwise nitrogen oxides or ammonia wouldemerge at the end. The following descriptionof the chemical processes explains why this isthe case.

Conversion of the urea-water solution

The uniform distribution of the urea-watersolution in the exhaust gas and the conversion

to ammonia take place in the exhaust pipeupstream of the SCR catalytic converter.

Initially, the urea ((NH2)2CO) dissolved in theurea-water solution is released.

The conversion of urea into ammonia takesplace in two stages.

36 - Nitrogen oxides

37 - Ammonia

38 - Urea-water solution

39 - Release of urea from theurea-water solution


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This means, only a part of the urea-watersolution is converted into ammonia duringthermolysis. The remainder, which is in the

form of isocyanic acid, is converted in asecond step.

The water required for this purpose is alsoprovided by the urea-water solution.

Therefore, following hydrolysis, all the urea isconverted into ammonia and carbon dioxide.

Thermolysis

Explanation: During thermolysis, the urea-water solution is split into two productsas the result of heating.

Initial product: Urea ((NH2)2CO)

Result: Ammonia (NH3)

Isocyanic acid (HNCO)

Chemical formula: (NH2)2CONH3+ HNCO

40 - Thermolysis: Urea converts to ammonia and isocyanic acid

Hydrolysis

Explanation: The isocyanic acid that was produced during thermolysis is convertedinto ammonia and carbon dioxide (CO2) by the addition of water in thehydrolysis process.

Initial products: Isocyanic acid (HNCO)

Water (H2O)

Result: Ammonia (NH3)

Carbon dioxide (CO2)

Chemical formula: HNCO + H2ONH3+ CO2

41 - Hydrolysis: Isocyanic acid reacts with water to form ammonia and carbon dioxide


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NOxreduction

Nitrogen oxides are converted into harmlessnitrogen and water in the SCR catalyticconverter.

It can be seen that each individual atom hasfound its place again at the end of the process,i.e. exactly the same elements are on the leftas on the right. This takes place only when theratio of the urea-water solution to nitrogenoxides is correct. Nitrogen oxides would

emerge if too little urea-water solution wereinjected. By the same token, ammonia wouldemerge if too much urea-water solution wereinjected, resulting in unpleasant odour andpossible damage to the environment.

42 - Nitrogen and water

Reduction

Explanation: The catalytic converter serves as a "docking" mechanism for theammonia molecules. The nitrogen oxide molecules meet theammonia molecules and the reaction starts and energy is released.This applies to NO in the same way as to NO2.

Initial products: Ammonia (NH3)

Nitrogen monoxide (NO)

Nitrogen dioxide (NO2)

Oxygen (O2)

Result: Nitrogen (N2)

Water (H2O)

Chemical formulae: NO + NO2+ 2NH32N2+ 3H2O

4NO + O2+ 4NH3 4N2+ 6H2O

6NO2+ 8NH3 7N2+ 12H2O

43 - NOxreduction: Nitrogen oxides react with ammonia to form nitrogen and water


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SCR control

The SCR control is integrated in the digitaldiesel electronics (DDE). The SCR control is

divided into the metering system control andthe metering strategy.

44 -


1 Digital diesel electronics DDE7 10 Pressure sensor

2 SCR control 11 Temperature sensor in activereservoir

3 Metering system control 12 Outside temperature sensor

4 Metering strategy 13 Level sensor in active reservoir

5 Injection pump 14 Level sensor in passive reservoir

6 Transfer pump 15 NOxsensor before SCR catalyticconverter

7 Metering module 16 NOxsensor after SCR catalyticconverter

8 Heater 17 Exhaust temperature sensor

9 Reversing valve


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Metering strategy

The metering strategy is an integral part of theSCR control that calculates how much area-water solution is to be injected at what time.

During normal operation, the signal from theNOxsensor before the SCR catalyticconverter is used for the purpose ofcalculating the quantity. This sensordetermines the quantity of nitrogen oxide inthe exhaust gas and sends the correspondingvalue to the DDE.

However, the NOxsensor must reach its

operating temperature before it can startmeasuring. Depending on the temperature,this can take up to 15 minutes. Until then theDDE uses a substitute value to determine theamount of nitrogen oxide in the exhaust gas.

A second NOxsensor is installed after theSCR catalytic converter for the purpose ofmonitoring the system. It measures whetherthere are still nitrogen oxides in the exhaustgas. If so the injected quantity of the urea-water solution is correspondingly adapted.The NOx sensor, however, measures not onlynitrogen oxides but also ammonia but cannot

distinguish between them.

If too much urea-water solution is injected,although the nitrogen oxides are completelyreduced so-called "ammonia slip" occurs, i.e.ammonia emerges from the SCR catalyticconverter. This in turn causes a rise in thevalue measured by the NOxsensor. The aim,

therefore, is to achieve a minimum of thesensor value.

This, however, is a long-term adaptation andnot a short-term control process as the SCRcatalyticconverterperforms a storagefunctionfor ammonia.

45 - Nitrogen and ammonia emission diagram

Index Explanation

A Value output by NOxsensor

B Injected quantity of urea-watersolution

1 Too little urea-water solutioninjected

2 Correct quantity of little urea-watersolution injected

3 Too much urea-water solutioninjected


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Metering system control

The metering system control could beconsidered as the executing part. It carries outtherequirements setby themeteringstrategy.This includes both the metering, i.e. injectionas well as the supply of the urea-watersolution.

The tasks of the metering system controlduring normal operation are listed in thefollowing:

Metering of the urea-water solution:

Implementation of the required targetquantity of urea-water solution

Feedback of the implemented actualquantity of urea-water solution.

Supplying urea-water solution:

Preparation ofmetering process (filling linesand pressure built-up)undercorrespondingambient conditions (temperature)

Emptying lines during afterrunning

Heater actuation.

In addition, the metering system controlrecognizes faults, implausible conditions orcritical situations and initiates corresponding

measures.

Metering of the urea-water solution

The metering strategy determines thequantity of urea-water solution to be injected.The metering system control executes thisrequest. A part of the function is meteringactuation that determines the actual openingof the metering valve.

Depending on the engine load, the meteringvalve injects at a rate of 0.5 Hz to 3.3 Hz.

The metering actuation facility calculates thefollowing factors in order to inject the correctquantity:

The duty factor of the actuator of themetering valve in order to determine theinjection duration

Actuation delay to compensate for thesluggishness of the metering valve.

The signal from the pressure sensor in themetering line is taken into account to ensurean accurate calculation; the pressure,however, should remain at a constant 5 bar.

The metering system control also calculatesthe quantity actually metered and signals thisvalue back to the metering strategy.

Themetering quantity is also determined overa longer period of time. This long-termcalculation is reset during refuelling or can bereset by the BMW diagnosis system.


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Supplying urea-water solution

A supply of a urea-water solution is requiredfor the selective catalytic reduction process. Itis necessary to store this medium in thevehicle and to make it available rapidly underall operating conditions. In this case 'makingavailable' means that the urea-water solutionis applied at a defined pressure at themetering valve.

Various functions that are described in thefollowing are required to carry out this task.

Heater

Thesystemmust be heatedas theurea-watersolution freezes at a temperature of -11 C.

The heating system performs following tasks:

To monitor the temperature in the activereservoir and the ambient temperature

To thaw a sufficient quantity of urea-watersolution and the components required formetering the solution during system start-up

To prevent the relevant componentsfreezing during operation

To monitor the components of the heatingsystem.

The following components are heated:

Surge chamber in active reservoir

Intake line in active reservoir

Delivery module (pump, filter, reversingvalve)

Metering line (from active reservoir tometering module).

The heating systems for the metering line anddelivery module are controlled dependent onthe ambient temperature.

The heater in the active reservoir is controlledas a function of the temperature in the activereservoir.

The heating control is additionally governedbythe following conditions:

Temperature in active reservoir and ambient temperature are the same

Condition 1 Condition 2 Condition 3 Condition 4

Ambient temperature andtemperature in active reservoir

> -4C < -4C < -5C < -9C

Metering line heater Not active Not active Active Active

Active reservoir heater Not active Active Active Active

Metering standby Established Established Established Delayed


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Metering standby is delayed at a temperaturebelow -9C in the active reservoir, i.e. adefined waiting period is allowed to elapseuntil an attempt to build up pressure begins.This time is constant from-9C to-16.5C asit is not possible to determine to what extentthe urea-water solution is frozen. Attemperatures below -16.5C, the heatingtime is extended until an attempt to build upthe pressure is made.

Heating the metering line generally takesplace muchfaster. Therefore, the temperature

in the active reservoir is the decisive factor forthe period of time until an attempt to build upthe pressure is undertaken. However, it ispossible that theheating time for the meteringline is longer at ambient temperatureconsiderably lowerthan thetemperature in theactive reservoir. In this case, the ambienttemperature is taken for the delay in meteringstandby.

The following graphic shows the delay as afunction of the temperature sensor signals.

The graphic shows that, with the sametemperature signals, the delay time relating tothe temperature in the active reservoir islonger than the delay caused by the ambienttemperature.

Only the times at temperatures below -9 Care relevant as they are shorter than 3 minutesat temperatures above -9C. 3 minutes is thetime that the entire system requires toestablish metering standby (e.g. also taking

into account the temperature in the SCRcatalyticconverter). This is also thetime that isapproved by the EPA (EnvironmentalProtection Agency) as the preliminary periodunder all operating conditions. This time is

extended significantly at very lowtemperatures.

The following example shows how the delaytime up to metering standby is derived at lowtemperatures.

46 - Diagram - meteringstandby delay times


A Delay as a function of temperature inactive reservoir

B Delay as a function of ambienttemperature

t [s] Delay time in seconds T [C] Temperature in degrees Celsius


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Transfer pumping

So-called transfer pumping is required sincetwo reservoirs are used for storing the urea-water solution. The term transfer pumping

relates to pumping the urea-water solutionfrom the passive reservoir into the activereservoir.

The following conditions must be met fortransfer pumping:

There isa urea-water solution in the passivereservoir

The ambient temperature is above aminimum value of -5 C for at least 10minutes

A defined quantity (300 ml) was used up inthe active reservoir or the reserve level inthe active reservoir was reached.

The solution is then pumped for a certain timein order to refill the active reservoir. Thetransfer pumping procedure is terminated ifthe "full" level is reached before the time haselapsed.

If the passive reservoir was refilled, transferpumping will only take place after a quantity ofapprox. 3 l has been used up in the activereservoir. The entire quantity is then pumpedover. The system then waits again until a

quantity of approx. 3 l has been used up in theactive reservoir before again pumping theentire quantity while simultaneously startingthe incorrect refilling detection function. Thisfunction determines whether the system hasbeen filled with the wrong medium as it ispresent in high concentration in the activereservoir.

Transfer pumping does not take place in theevent of a fault in the level sensor system.

47 - Transfer pumping

Index Explanation Index Explanation1 Passive reservoir 6 Pump

2 Level sensors 7 Non-return valve

3 Extractor connections 8 Level sensor

4 Transfer line 9 Active reservoir

5 Filter


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Delivery

The urea-water solution is delivered from theactive reservoir to the metering module. Thistask is performed by a pump that is integratedin the delivery unit. The delivery unitadditionally contains:

Heater

Pressure sensor

Filter

Return throttle

Reversing valve.

The pump is actuated by a pulse-widthmodulated signal (PWM signal) from the DDE.The PWM signal provides a speedspecification for the purpose of establishingthe system pressure. The value for the speedspecification is calculated by the DDE basedon the signal from the pressure sensor.

When the system starts up, the pump isactuated with a defined PWM signal and theline to the metering module is filled. This isfollowed by pressure build-up. Only then doespressure control take place.

48 - Delivery


1 Metering line 8 Filter

2 Delivery module 9 Level sensor

3 Pump 10 Filter

4 Reversing valve 11 SCR catalytic converter

5 Filter 12 Exhaust system

6 Restrictor 13 Metering module

7 Pressure sensor


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When the metering line is filled, the openedmetering valve allows a small quantity of theurea-water solution to be injected into theexhaust system.

During pressure control, i.e. during normaloperation with metering, the pump is actuatedinsuch a way thata pressureof 5 bar isappliedin the metering line. Only a small part of theurea-water solution delivered by the pump isactually injected.Themajorityof thesolution istransferred via a throttle back into the activereservoir. This means, the delivery pressure isdetermined by the pump speed together with

the throttle cross section.

Thesolution is injected four times per second.The quantity is determined by the openingtime and stroke of the metering valve.However, the quantity is so low that there is nonoticeable drop in pressure in the meteringline.

Evacuating

After turning offthe engine, thereversing valveswitches to reverse the delivery direction ofthe pump, thus evacuating the metering lineand metering module.

49 - Evacuating

Index Explanation Index Explanation1 Metering line 8 Filter

2 Delivery module 9 Level sensor

3 Pump 10 Filter

4 Reversing valve 11 SCR catalytic converter

5 Filter 12 Exhaust system

6 Throttle 13 Metering module

7 Pressure sensor


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SCR system modes

When the ignition is switched on, the SCRcontrol undergoes a logical sequence ofmodes in the DDE. There are conditions thatinitiate the change from one mode to the

other. The following graphic shows thesequence of modes which are subsequentlydescribed.

51 - Sequence of modes in SCR control


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INIT (SCR initialization)

The control unit is switched on (terminal 15ON) and the SCR system is initialized.

STANDBY (SCR not active)

STANDBY mode is assumed either afterinitialization or in the case of fault.

AFTERRUNmode is assumed if terminal 15 isswitched off in this state or a fault occurs.

NOPRESSURECONTROL (waiting forenable for pressure control)

NOPRESSURECONTROL mode is assumedwhen no faults occur in the system. In thismode, the system is waiting for the pressurecontrol enable that is providedby thefollowingsensor signals:

Temperature in catalytic converter

Temperature in active reservoir

Ambient temperature

Engine status (engine running).

The system also remains in

NOPRESSURECONTROL mode for aminimum period of time so that a plausibilitycheck of the pressure sensor can beperformed.

PRESSURECONTROL mode is assumedonce the enable is finally given.

STANDBY mode is assumed if terminal 15 isswitched off or a fault occurs inNOPRESSURECONTROL mode.

PRESSURECONTROL (SCR systemrunning)

PRESSURECONTROL mode is the normaloperating status of the SCR system and hasfour submodes.

PRESSURECONTROL mode is maintaineduntil terminal 15 is switched off. A change toPRESSUREREDUCTION mode then takes

place.A change to PRESSUREREDUCTION modealso takes place if a fault occurs in the system.

The four submodes ofPRESSURECONTROL are described in thefollowing:

REFILL

The delivery module, metering line and themetering module are filled when REFILLmode is assumed. The pump is actuatedand the metering valve opened by a definedvalue. The fill level is calculated.

The mode changes toPRESSUREBUILDUP whenthe required filllevel is reached or a defined pressureincrease is detected.

PRESSUREREDUCTION mode isassumed if terminal 15 is switched off or afault occurs in the system.


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PRESSUREBUILDUP

In this mode, the pressure is built up to acertain value. For this purpose, the pump isactuated while the metering valve is closed.

If the pressure is built up within a certaintime, the system switches to the next modeof METERINGCONTROL. If the requiredpressure built-up is not achieved after thedefined period of time has elapsed, a statusloop is initiated, andVENTILATIONmode isassumed.

If the pressure cannot be built up after a

defined number of attempts, the systemsignals a fault and assumesPRESSUREREDUCTION mode.

PRESSUREREDUCTION mode is alsoassumed when terminal 15 is switched offor another fault occurs in the system.

VENTILATION

If the pressure could not be increasedbeyond a certain value inPRESSUREBUILDUP mode, it is assumedthat there is still air in the pressure line.

The metering valve is opened for a definedperiod of time to allow this air to escape.This status is exited after this time haselapsed and the system returns toPRESSUREBUILDUP mode. The loop

between PRESSUREBUILDUP andVENTILATION varies corresponding to theconditionof thereducing agent.Thereasonfor this is that a different level is establishedafter REFILL depending on the ambientconditions. Repeating the ventilationfunction will ensure that the pressure line iscompletely filled with reducing agent.

PRESSUREREDUCTION mode isassumed if terminal 15 is switched off or afault occurs in the system.

METERINGCONTROL

The system can enable metering inMETERINGCONTROL mode. This is theactual status during normal operation. Theurea-water solution is injected in this mode.

In this mode, the pump is actuated in sucha wayth

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